How to make my hillshade bright as given in the link?
This is matter of lights in your settings as also said susu in the comments.
Just an example from your file (but with another texture because you did not pack your texture in the file).

Only things changed are the lights.
I've changed the point light by a sun light and gave it an orientation and a strength of one (= one solar unit, our sun).

And added an environment texture (you can take hdri textures from Blender's install directory, in the data part):

From that, up to you changing color, texture, light intensity, etc.